Thermal behavior of concentrated oil-in-water emulsions based on soybean oil and palm kernel olein blends

Droplet size distribution and thermal behavior of concentrated oil-in-water emulsions based on soybean oil (SBO)/palm kernel olein (PKO) blends were investigated. The emulsions were prepared using 70% (wt./wt.) oil blends of SBO/PKO as dispersed phases and stabilized by egg yolk. An increase in PKO level (0–40% wt./wt.) in the oil dispersed phase volume fraction caused significant increases (p < 0.05) in volume-weighted mean diameter (d_4,3). The DSC data suggested that crystallization of the emulsions was induced by a ‘template effect’ of yolk constituents via a surface heterogeneous nucleation. Emulsions with 0–20% (wt./wt.) PKO levels in the dispersed phase demonstrated a good cool–heat stability even after three successive thermal cycles (from 50 °C to ?70 °C at 10 min/°C). After the first thermal cycle, emulsions with 30% and 40% PKO levels in the oil dispersed phase were destabilized due to strong coalescence and crystallized via volume-surface heterogeneous nucleation. The unstable emulsions were attributable to high level of saturated triacylglycerols from PKO, with high droplet size characteristic, causing them to be more prone to partial coalescence.     

Compositional and thermal characteristics of palm olein-based diacylglycerol in blends with palm super olein

Palm olein-based diacylglycerol (POL-DAG) was blended with palm super olein (POoo) in various concentrations (10–90%), with increments of 10% (wt/wt) POL-DAG. The physical and chemical characteristics, i.e., iodine value, acylglycerol content, fatty acid composition, melting and crystallization profiles and solid fat content, for POL-DAG, POoo and their binary blends were evaluated. The mid-infrared FTIR was used to determine the absorption bands of the different concentrations of the oil blends. Only slight differences of FAC and IV were observed. POL-DAG:POoo blends showed significant changes (p < 0.05) in DAG content and decreases in TAG content with increasing POL-DAG content. The DSC thermograms showed that the addition of different concentrations of POL-DAG changed the melting and crystallization behavior of the oil blends (POL-DAG:POoo). The crystallization onset point increased (p < 0.05) with an increasing POL-DAG concentration (10–90%). POL-DAG has the same absorption bands as POoo, with the exception of several minor peaks that appeared at (I) 2954 cm^− 1, (II) 1267 cm^− 1, (III) 1199 cm^− 1, (IV) 1222 cm^− 1 and (V) 966 cm^− 1. This study will provide essential information for the palm oil industry to identify the most suitable POL-DAG blends with desirable physicochemical properties for food application purposes.     

Effects of variation in the palm stearin: Palm olein ratio on the crystallisation of a low-trans shortening

Changes in the rheological properties during crystallisation and in the crystal size and morphology of blends containing rapeseed oil with varying percentages of palm stearin (POs) and palm olein (POf) have been studied. The crystals formed from all three blends were studied by confocal laser scanning microscopy, light microscopy and environmental scanning electron microscopy, which revealed the development of clusters of 3–5 individual elementary “spherulites” in the early stages of crystallisation. The saturated triacylglycerol content of the solid crystals separated at the onset of crystallisation was much greater than that in the total fat. Fat blends with a higher content of palm stearin had a more rapid nucleation rate when observed by light microscopy, and this caused an earlier change in the rheological properties of the fat during crystallisation. Using a low torque amplitude (0.005 Pa, which was within the linear viscoelastic region of all samples studied) and a frequency of 1 Hz, the viscoelastic properties of melted fat during cooling were studied. All samples, prior to crystallisation, showed weak viscoelastic liquid behaviour (G″, loss modulus >G′, storage modulus). After crystallisation, a more “solid like” behaviour was observed (G′ similar to or greater than G″). The blend having the highest concentration of POs was found to have the earliest onset of crystallisation (27% w/w POs; 12 mins, 22% w/w POs; 13.5 mins, 17% w/w POs, 15 mins, respectively). However, there were no significant differences in the time to the point when G′ became greater than G′ among the three blends.     

In search of confectionary fat blends stable to heat: Hydrogenated palm kernel oil stearin with sorbitan monostearate

The potential of sorbitan monostearate (SMS) addition to change the basic-crystal-structure of a confectionary fat blend (CFB) with the aim to enhance its heat resistance was investigated. The CFB used in this study was a blend of hydrogenated palm kernel oil stearin, lecithin, polyglycerol polyricinoleate (PGPR) and cocoa butter. Samples made with different proportions of SMS to CFB were prepared and the crystal structure, the melting behaviour, the crystal morphology and crystallization kinetics were studied. Heat resistance was evaluated using a temperature-variable rheological method. Powder X-ray diffraction (XRD) studies in the wide angle region (WAXS) revealed the presence of two crystalline polymorphs (α and β′) in all blends. While XRD studies in the small angle region (SAXS) revealed a shift in the CFB peak position upon addition of SMS. The presence of two polymorphic forms was confirmed by differential scanning calorimetry (DSC), while a third endotherm was evident when the amount of SMS present in the system was greater than 40%. Studies on the nucleation and crystallization kinetics showed that crystal nucleation and growth occurred in two stages: SMS appeared first followed by CFB. Iso-solid diagrams constructed from the melting profiles obtained from SFC-temperature measurements indicated monotectic solution behaviour between SMS and the CFB.The microstructure, as observed under polarized light, changed from small crystals for the CFB to needles for mixtures with 10% SMS, to spherulites for mixtures with 50% SMS, to clusters for mixtures containing between 80 and 100% SMS. Cryo-TEM showed nanoplatelet formation for the CFB and nano-blobs for SMS. The storage modulus (G′) for mixtures containing 25% SMS decreased from G′ = 1.72 10⁷ ± 4.60 10⁶ Pa at 20 °C to G′ = 3.24 10⁵ ± 2.15 10⁴ Pa at 40 °C. Thus, SMS addition to confectionery fats can provide heat resistance to the CFB.     

On the fractional crystallization of palm olein: Solid solutions and eutectic solidification

In this contribution, the nature of particular crystal growth behavior observed in industrial dry fractionation of palm olein is further elucidated. Refined palm olein was prepared with three different concentrations of tripalmitoyl-glycerol (0.6%, 0.8% and 1%) and crystallized under stirring at 13, 15 and 17 °C to study the effect of internal seeding with tripalmitoyl-glycerol (PPP) on bulk crystallization properties. Notably at 15 °C, the increase in the solid fat content of the crystal suspension as function of time was heavily promoted by higher PPP-contents. The resulting crystals displayed a broad melting peak between 28 and 40 °C in DSC-measurements, which suggested the presence of a solid solution in a metastable form, mainly consisting of PPP and dipalmitoyl-oleoylglycerol (POP). SAXS-measurements supported this thesis by revealing long spacings with varying length, while short spacings obtained in WAXD consistently indicated the orthorhombic subcell of a β′-polymorph. The data suggest that the internal seeding effect of PPP in palm olein, as applied in industrial crystallization, in fact relies on substantial miscibility with POP, rather than on a heterogeneous nucleation effect resulting in two separate crystalline phases. The miscibility of PPP and POP then would result in a facilitated alignment of POP-molecules in the direction of the methyl end (or lamellar) plane and higher growth rates. Secondly, a peculiar change in crystal morphology could be consistently linked with the occurrence of a sharp melting peak at 24 °C in DSC, as well as with a substantial increase of the viscosity of the crystal suspension. This morphological shift concurred with an increased incorporation of palmitoyl-oleoyl-stearoylglycerol in the lattice, possibly giving rise to eutectic crystallization in lamellar crystal structures instead of the commonly observed dendritic crystals. The clarification of both phenomena provides a valuable, profound insight in the crystal growth step in the processing of edible oils.     

Stability and rheology of concentrated O/W emulsions based on soybean oil/palm kernel olein blends

Droplet size distribution and rheological properties of egg yolk-stabilized emulsions were studied before and after storage (25 °C, 30 days). The dispersed phase (70%) of the emulsions was based on soybean oil (SBO) and 10–40% palm kernel olein (PKO) replacements of SBO. Replacement of PKO resulted in a significant increase in droplet mean diameters and a decrease in rheological properties of the emulsions. All emulsion exhibited a gel-like characteristic with storage modulus higher than loss modulus and tan δ greater than 0.3. Significant increase (p < 0.05) was found for droplet mean diameters and rheological properties of the emulsions after storage. Emulsion with fully SBO and the highest PKO replacement (40%) were found to be the most unstable, which was ascribed to a strong flocculation. With 10–30% PKO replacements, the emulsions displayed a better stability after storage, most probably promoted by significant content of short-medium chain fatty acids in PKO.     

Effects of chemical interesterification on physicochemical properties of blends of palm stearin and palm olein

Chemical interesterification is an important technological option for the production of fats targeting commercial applications. Fat blends, formulated by binary blends of palm stearin and palm olein in different ratios, were subjected to chemical interesterification. The following determinations, before and after the interesterification reactions, were done: fatty acid composition, softening point, melting point, solid fat content and consistency. For the analytical responses a multiple regression statistical model was applied. This study has shown that blending and chemical interesterifications are an effective way to modify the physical and chemical properties of palm stearin, palm olein and their blends. The mixture and chemical interesterification allowed obtaining fats with various degrees of plasticity, increasing the possibilities for the commercial use of palm stearin and palm olein.     

Discrimination of palm olein oil and palm stearin oil mixtures using a mass spectrometry based electronic nose

To discriminate mixing ratios for mixtures of palm olein oil and palm stearin oil, an electronic nose based on mass spectrometer (MS-electronic nose) and GC were used. The intensities of each fragment from the palm olein oil and palm stearin oil by the MS-electronic nose were used for discriminant function analysis (DFA). When palm olein oil is mixed with palm stearin oil, more than 3% of stearin oil can be estimated by DFA. The obtained data were used for DFA. DFA plot indicated a significant separation of pure palm olein oil and palm stearin oil. The added concentration of palm stearin oil to palm olein oil was highly correlated with the first discriminant function score (DF1). When palm stearin oil was added to palm olein oil, it was possible to predict the following equation; DF1= −0.112×(conc. of palm stearin oil)+0.416 (r²=0.95). When palm stearin oil was added to palm olein oil, peak area of GC was correlated to DF1 by MS-electronic nose with ratio of palm olein oil vs palm stearin oil. The MS-electronic nose system could be used as an efficient method for the authentication of oil.     

Kinetic analysis of isothermal crystallization in hydrogenated palm kernel stearin with emulsifier mixtures

The kinetics of isothermal crystallization of hydrogenated palm kernel stearin (HPKS) with emulsifiers was evaluated by applying the Avrami equation. Effects of five commercial emulsifiers (lecithin, monoglyceride, polyglycerol polyricinoleate, Span 60, and Tween 60) on crystallization behaviors were tested at four different isothermal temperatures (15, 20, 25, and 30 °C). It is shown that, as temperature increases, induction time for HPKS samples generally increased especially from 25 to 30 °C. Meanwhile, different nucleation mechanisms were observed according to Avrami exponent (n) values. The addition of emulsifiers generally accelerated crystallization rate without changing the growth mechanism (plate-like growth) under 25 °C. However, when the temperature increased to 30 °C, n ranged from 1.0 to 5.1, which indicated different nucleation mechanisms induced by different emulsifiers. Avrami constant (k) (indicating the crystallization rate) decreased as the temperature increased except for samples with Span 60. At higher temperatures, values of t_1/2 were significantly higher which reflects the decrease in k at higher temperatures. Crystal microstructures at 30 °C were obtained by using polarized light microscope. Lecithin and Span 60 samples showed large and dense crystals compared with the control sample. Tween 60 sample showed very small crystals which aggregated in a line trend. However, small differences were observed in fractal dimension results except for Tween 60 sample.     

Effects of high intensity ultrasound and emulsifiers on crystallization behavior of coconut oil and palm olein

The objective of this research is to evaluate the crystallization behavior of coconut oil (CO) and palm olein (PO) as affected by the addition of two monoacylglycerols (MAG) emulsifiers and by the use of high intensity ultrasound (HIU). MAG with high content of palmitic, oleic, and linoleic acid (EM1) and MAG with high content of stearic acid and no unsaturated fatty acids (EM2) were used. Results show that the addition of emulsifiers did not affect crystallization kinetics of CO and similar solid fat contents (1.32 ± 0.94) (SFC) and melting enthalpies (5.90 ± 4.56) were obtained. The addition of EM1, however, significantly delayed the crystallization of PO as evidenced by a significantly lower SFC and melting enthalpy. SFC for PO was 8.56 ± 0.913 while SFC for PO + EM1 was 3.63 ± 1.38. Sonication induced the crystallization of CO samples crystallized with and without EM1 and EM2 while only induced the crystallization of PO + EM1 as measured with SFC. The induction in crystallization by HIU was also evidenced by higher enthalpy with values up to a range of 8 J/g to 11 J/g. A decrease in elasticity from 3.17 × 10⁶ to 2.52 × 10⁵ was observed in CO crystallized with emulsifiers which could be reverted by the application of HIU. Contrarily, the addition of emulsifiers increased elasticity of PO from 3.35 × 10² to 4.83 × 10⁴ and sonication did not affect these values significantly. Differences observed in elasticity values are attributed not only to the amount of solid material obtained but also to the type of microstructure of the crystalline network formed during crystallization.     

Phenolic profile and antioxidant activity of the Algerian ripe date palm fruit (Phoenix dactylifera)

The aim of this study was to determine the phenolic profile of seven different varieties of ripe date palm fruit (Phoenix dactylifera) from Algeria by LC–DAD–MS (ESI+), to investigate their respective antioxidant activities by the DPPH^· method and to estimate their phenolic content using the Folin–Ciocalteu method. The total phenolic content was in the range of 2.49 ± 0.01 to 8.36 ± 0.60 mg gallic acid equivalents (GAE) per 100 g fresh fruit. This fruit was shown to possess an antioxidant activity, giving values of antiradical efficient (AE) from 0.08 ± 0.00 to 0.22 ± 0.00. The phenolic contents and the antiradical efficiencies of the different varieties were highly correlated (R²=0.975). All the varieties were found to contain mainly p-coumaric, ferulic and sinapic acids and some cinnamic acid derivatives. Three different isomers of 5-o-caffeoylshikimic acid were detected. Different types of flavonoids were identified, mainly flavones, flavanones and flavonol glycosides.     

Flow properties of table margarine prepared from lipase-catalysed transesterified palm stearin:palm kernel olein feedstock

The flow properties of an experimental table margarine prepared from Rhizomucor miehei lipase-catalysed transesterified palm stearin:palm kernel olein (PS:PKO) blend at 40:60 was stored for 3 months at test temperatures of 20 and 30°C and determined using a controlled-rate rheometer. A commercial table margarine was used as a comparison. The shear stress-shear rate data was represented well by the Herschel–Bulkley model (r > 0.99). The mean yield stress values during storage were the highest for the experimental table margarine. However, the effect of storage on the mean yield stress was insignificant (p > 0.001). The Power Law model with a yield stress also represented the margarine flow well (r > 0.99) and the Power Law intercepts and slopes were also the highest for the experimental margarines, indicating a higher degree of firmness in the experimental samples. Storage effect was also insignificant (p > 0.05).     

Evaluation of shortenings based on various palm oil products

Several formulations based on blends of hydrogenated palm oil (MP 41·5°C) and palm stearin (IV 44) with other liquid oils, on direct blends of palm stearin with other liquid oils, and on 100% inter-esterified palm olein, were used as feedstocks in shortening production. The shortenings were stored at 20°C over a period of one month. Physicochemical characteristics, creaming properties and baking performance of the shortenings were evaluated and compared with the best shortening on the market. Slip melting point of the shortenings ranged from 41·5 to 46·4°C. Palm-cottonseed oil shortenings had higher solid fat contents at all temperatures than palm-soya bean or palm-low erucic acid rapeseed oil shortenings. The shortenings were rich in C₅₀, C₅₂and C₅₄ glycerides. Creaming power after 12 min of beating ranged from 1·55 to 1·77 cm³ g^?1. Palm stearin-cottonseed (3:2) oil shortening showed the best creaming performance. The specific volume of cakes ranged, for the experimental shortening, from 90% to 101% from the control, with low erucic acid-palm blends showing the best performance. In applications for both aerated cream and cakes, inter-esterified palm olein was excellent.     

Sensory evaluation of egg products and eggs laid from hens fed diets with different fatty acid composition and supplemented with antioxidants

Is the sensory quality of eggs influenced by adding vegetable lipids, animal and vegetable sources of n − 3 polyunsaturated fatty acids (n − 3 PUFA), and/or natural antioxidants to the hens diet? To answer this question three feeding experiments were conducted adding either palm butter, grape seed oil, flax seed oil, n − 3 PUFA such as flax seed and marine algae and the natural antioxidant rosemary to the hens diet. For each experiment a standard diet was used as control. The results suggested that vegetable lipids (palm butter, grape seed, flax seed), n − 3 PUFA (flax seed and marine algae) and rosemary may be used to hens fed diet without affecting the sensory properties of eggs.The sensory quality of eggs was evaluated on hard boiled, scrambled eggs and Madeira cake.In this work, we report the first sensory characterization of eggs and products containing eggs obtained from hens diet based on grape and algae plus vitamin E and rosemary extract.     

Preparation of palm olein enriched with medium chain fatty acids by lipase acidolysis

Medium chain (MC) fatty acids, caprylic (C8:0) and capric (C10:0) were incorporated into palm olein by 1,3-specific lipase acidolysis, up to 36% and 43%, respectively, when added as mixtures or individually after 24 h. It was found that these acids were incorporated into palm olein at the expense of palmitic and oleic acids, the former being larger in quantity and reduction of 18:2 was negligible. The modified palm olein products showed reduction in higher molecular weight triacylglycerols (TGs) and increase in concentration of lower molecular weight TGs compared to those of palm olein. Fatty acids at sn-2 position in modified products were: C10:0, 4%; C16:0, 13%; C18:1, 66%; and C18:2, 15.4%. DSC results showed that the onset of melting and solids fat content were considerably reduced in modified palm olein products and no solids were found even at and below 10 °C and also the onset of crystallisation was considerably lowered. The cloud point was reduced and iodine value dropped from 55.4 to 38 in modified palm olein. Thus, nutritionally superior palm olein was prepared by introducing MC fatty acids with reduced palmitic acid through lipase acidolysis.     

Physico-chemical properties of various palm-based diacylglycerol oils in comparison with their corresponding palm-based oils

Palm-based diacylglycerol (P-DAG) oils were produced through enzymatic glycerolysis of palm kernel oil (PKO), palm oil (PO), palm olein (POL), palm mid fraction (PMF) and palm stearin (PS). High purity DAG (83–90%, w/w) was obtained and compared to palm-based oils (P-oil) had significantly (P < 0.05) different fatty acid composition (FAC), iodine value (IV) and slip melting point (SMP). Solid fat content (SFC) profiles of P-DAG oils as compared to P-oils had less steep curves with lower SFC at low temperature range (5–10 °C) and the higher complete melting temperatures. Also, P-DAG oils in contrast with P-oils showed endothermic as well as exothermic peaks with higher transition temperatures and significantly (P < 0.05) higher crystallisation onsets, heats of fusion, and heats of crystallisation. Crystal forms for P-DAG oils were mostly in the β form.     

Physicochemical and Sensory Properties of Instant Kunun-Zaki Flour Blends from Sorghum and Mango Mesocarp Flours

Instant Kunun-zaki, a fermented non-alcoholic sorghum beverage, was prepared by mixing different per cent blend ratios of unmalted sorghum flour: mango mesocarp flour (90:0, 75:15, 70:20, 65:25, and 60:30) with 10% malted sorghum. Proximate compositions, chemical and functional properties of the blends were analyzed. Addition of mango mesocarp flour significantly (p ≤ 0.05) increased the ash (1.31 to 1.75%), crude fibre (2.57 to 3.39%) and decreased significantly (p < 0.05) the energy content (368.21 to 354.67 kcal/100 g) of the blends. The β-carotene content also increased from 95.65 to 139.13 μg/100 g with increased mango mesocarp flour. Hygroscopicity increased significantly (p < 0.05) from 6.10 to 10.28% while viscosity of the blends decreased significantly (p < 0.05) from 1715 to 1195.46 cP. Mango mesocarp flour addition increased the ash, crude fibre and introduced β-carotene into the product.     

Effect of the addition of palm stearin and storage temperatures on the thermal properties of glycerol monostearate-structured emulsions

Monoglyceride (MG) structured oil-in-water emulsions have been developed as low fat shortening alternatives. In this work, the effect of the addition of palm stearin (PS) and storage at different temperatures on the thermal properties of glycerol monostearate (GMS)-structured emulsions were characterized. The melting profile and the dropping point of GMS-structured emulsions were investigated during five weeks of storage at 8 °C and 22 °C. Results showed that the addition of PS changed the melting profiles of GMS-structured emulsions that were stored under refrigeration temperatures, possibly by reducing phase separation between GMS and co-emulsifiers. Storage at refrigeration temperatures increased the stability of the α-gel phase while storing at room temperatures accelerated emulsion destabilization. Even though samples stored at refrigeration temperatures had lower dropping points, they were in the α-gel phase, making refrigeration temperatures the desirable storage condition to achieve maximal stability of MG-structured emulsions.     

Intra- and interspecific mineral composition variability of commercial instant coffees and coffee substitutes: Contribution to mineral intake

The present paper reports the amount and estimated daily mineral intake of nine elements (Ca, Mg, K, Na, P, Fe, Mn, Cr and Ni) in commercial instant coffees and coffee substitutes (n = 49). Elements were quantified by high-resolution continuum source flame (HR-CS-FAAS) and graphite furnace (HR-CS-GFAAS) atomic absorption spectrometry, while phosphorous was evaluated by a standard vanadomolybdophosphoric acid colorimetric method.Instant coffees and coffee substitutes are rich in K, Mg and P (>100 mg/100 g dw), contain Na, Ca and Fe in moderate amounts (>1 mg/100 g), and trace levels of Cr and Ni. Among the samples analysed, plain instant coffees are richer in minerals (p < 0.001), except for Na and Cr. Blends of coffee substitutes (barley, malt, chicory and rye) with coffee (20–66%) present intermediate amounts, while lower quantities are found in substitutes without coffee, particularly in barley.From a nutritional point of view the results indicate that the mean ingestion of two instant beverages per day (total of 4 g instant powder), either with or without coffee, cannot be regarded as important sources of minerals to the human diet, although providing a supplementation of some minerals, particularly Mg and Mn in instant coffees. Additionally, and for authentication purposes, the correlations observed between some elements and the coffee percentage in the blends, with particular significance for Mg amounts, provides a potential tool for the estimation of coffee in substitute blends.     

Crystallization properties of palm oil by dry fractionation

The crystallization, thermal, physical, chemical and morphological properties of palm oil were investigated using differential scanning calorimetry, polarized microscopy, pulsed nuclear magnetic resonance (NMR) and gas chromatography (GC). The palm oil was fractionated into various stearin and olein (with iodine values (IV)>63) fractions by means of a dry fractionation process. During the cooling sequence, samples were taken at regular intervals from the crystallizer and analyzed for their iodine values, chemical compositions and physical behaviour. The physical properties of olein and stearin fractions, such as cloud point, slip melting point and solid fat content, were dependent on the crystallization temperatures. The iodine values of the olein and stearin fractions increased as the crystallization temperature decreased and both fractions started to cloud at lower temperatures. The palmitic acid content of stearin and olein fractions was also affected by the crystallization temperatures.